1. Field of the Invention
This invention relates to novel polyamide-imides and to methods for their preparation and is more particularly concerned with polyamide-imides derived from 2,2-bis[4-(p-aminophenoxy)phenyl]propane or the corresponding diisocyanate and with methods for their preparation.
2. Description of the Prior Art
Polyamides and polyimides derived from aromatic polycarboxylic acids and 2,2-bis[4-(p-aminophenoxy)phenyl]propane are known. Solvent soluble polyimides derived from aromatic tetracarboxylic acids (or anhydrides) and certain ether-sulfone diamines are described in U.S. Pat. No. 3,563,951. It is there disclosed that a minor proportion of the ether-sulfone diamine can be replaced by any one of a number of other diamines, including 2,2-bis[4-(p-aminophenoxy)phenyl]propane, without detracting from the solvent soluble properties of the polyimide.
It has been found, however, that the polyimides prepared from aromatic tetracarboxylic acids and 2,2-bis[4-(p-aminophenoxy)phenyl]propane alone lack the solvent solubility and, more particularly, are not melt processable, i.e. they are not useful in the preparation of extruded or injection molded parts.
The preparation of polyamides from aromatic dicarboxylic acids and 2,2-bis[4-(p-aminophenoxy)phenyl]propane is described in U.S. Pat. No. 3,505,288. Such polyamides also suffer from lack of melt processability and cannot be extruded or injection molded to give useful mechanical parts.
The present invention is based on the finding that polyamide-imides derived from trimellitic acid or anhydride and 2,2-bis[4-(p-aminophenoxy)phenyl]propane or the corresponding diisocyanate are melt processable, unlike very closely related polyamides, on the one hand, and closely related polyimides on the other, and can be used to prepare mechanical parts having good properties by injection molding techniques.